HEMOPHILIA

How is hemophilia diagnosed

?

Prolonged PTT (

Prothrombin thromboplastin time

) with a normal PT (

Prothrombin time

) and normal bleeding time is suggestive of hemophilia. It is confirmed by doing the factor assay.

Prenatal diagnosis

Chorionic villus biopsy at 8 weeks gestation on amniocentesis at 12-14 weeks can be used for prenatal diagnosis by DNA analysis if the mother's carrier state is demonstrated either by mutation analysis or Restriction Fragment Length polymorphism study. If DNA analysis is not available, fetal blood can be aspirated at 18-20 weeks gestation. If pure fetal blood is obtained, factor VIII activity can be assayed. If fetal blood mixed with amniotic fluid is obtained, factor VIII: Ag can be measured.

Carrier detection

Most carriers have a factor VIII level between 30-70 U/dl. Factor VIII levels should be assayed in all females who might be carriers to identify those with levels below 30U/dL. These women should be treated the same way as male hemophiliac with similar factor levels.

Assays of factor VIII activity and VWF: Ag can be used to predict whether a given woman is a carrier. If the factor VIII level is below normal, then she is designated as a true carrier. If her factor VIII level is in the normal range, but her VWF :Ag is higher, then she is a true carrier.

When a definite diagnosis of the carrier state can not be made, the probability of being a carrier is calculated from family tree analysis.

Recently, carrier identification can be done by examination of factor VIII gene and DNA analysis and Restriction fragment length polymorphisms

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